This invention relates to backup protection for sealed structural expansion joints, and particularly to retrofitted backup protection of structural members against water seeping around seals at expansion joints of elevated structures such as bridges or decks.
Elevated roadways with steel or concrete-steel superstructures generally sit on concrete piers with steel bearings. Such roadways expand and contract continuously with hourly changes in temperature, as well as seasonal temperature variations. They also move in response to other forces. Expansion joints, forming gaps between sections of roadway that rest on the pier caps, accommodate this movement, growth, and shrinkage. The expansion joints usually extend transversely across tho road, but may also follow longitudinally along the roadway. To prevent run-off water from damaging the supporting piers and caps, the expansion joints include elastically compressible seals secured in the gaps between the roadway sections. These seals shunt most of the water and other liquid materials that accumulate on a roadway away from gaps. The seals themselves resiliently reshape to fill the gaps between the roadway sections.
However, the seals are not perfect. Some of the water, caused by rain and snow and accompanying oils and other materials from leaking automobiles, pass by the seals and ultimately damage the structural piers and bearings supporting the roadway. Because the damage is so slow, it may not be recognized before the conditions become unsafe.
U.S. Pat. No. 4,804,292 illustrates a run-off arrangement for deflecting and collecting water seepage from the seals and diverting it to the sides of the roadway beyond the underlying piers and bearings. However, it is necessary to incorporate the run-off system into the bridge structure during initial construction, or to make it part of a dramatic rehabilitation project.
Accordingly, existing roadways cannot benefit from such a run-off system without reconstruction.